Fumehood with auxiliary air supply



March 1, 1966 J. BAYERN FUMEHOOD WITH AUXILIARY AIR SUPPLY v R m m n r NA w m NH N 2 W w E A B W H w w 5 O J FIG.5

United States Patent "ice 3,237,548 FUMEI-IOOD WITH AUXILIARY AIR SUPPLYJoseph Bayern, Hicksville, N.Y., assignor to Joseph Bayern and Jean A.Bayern, Hicksville, N.Y., joint tenants Filed Jan. 23, 1964, Ser. No.339,633 7 Claims. (Cl. 98--115) This invention relates to fumehoodshaving auxiliary air supply to supplement the room air so that a minimumof room air will be drawn into the hood in its operation. In particular,this invention relates to a fumehood having a face opening with a sashclosure and having an auxiliary air supply which is supplied fromoutside of the circumference or perimeter of the top and sides of theface or sash opening of the device.

Prior to my invention, various types of fumehoods were well known andused for the purpose of drawing off undesirable gases, fumes or othersubstances which might poison or pollute the air, for the purpose ofproviding breatheable air around the working area or Working chamberassociated with the fumehood.

Originally, fumehoods comprised a working chamber having an open frontand means usually at the top of the chamber to exhaust air andundesirable gases or other substances from the chamber. This wouldpermit a person or technician to conduct experiments and other processeswithin the chamber, and be free from the danger of inhaling theundesirable gases because the force of the exhaust would remove air fromthe room in which the fumehood was located through the working chamber,thence through the exhaust duct, carrying the undesirable gases and notpermitting them to enter the room. It was then desirable to provide atransparent protective shield through which the technician could observethe reactions taking place within the fumehood. Such a transparentshield is in the form of a strong glass such as a safety glass or wiredglass, and is placed within a sash so that the shield may be moved up ordown to provide access to the working chamber.

In conventional fumehoods, closing the shield would reduce the intakearea at the face of the working chamber until the intake area would becompletely closed and block further flow of air. Thus, provision wasmade, by means of a grille or other opening, to provide for flow of airand continued operation of the device through a by-pass other than theface opening, even though the glass sash was completely closed. In orderto overcome the correlated problem of changing the rate of flow of airby enlarging and reducing the size of the front opening of the chamberby raising and lowering the sash, an open grille of substantially thesame size as the front opening of the chamber was placed above the frontopening and communicating with the working chamber through the by-pass.The sash, which would be just large enough to cover the front opening,or the grille (or by-pass), could then be moved up and down tocompletely cover the grille (or by-pass) or completely cover the faceopening, or in any intermediate position partially to cover the grille(or by-pass) and the front opening simultaneously. In this way, thatportion of the front opening which would be reduced by the sash would becompensated for by a corresponding portion of the grille which would beuncovered as the sash was lowered.

Thus, air would be removed from the room at a constant rate of flow,whether the sash was up or down. This prevents high air velocities atthe lower level of the working chamber which are undesirable. Thus, theconstant volume fumehood, as these hoods are called, which may beoperated without creating undesirable velocities, even with the sashsubstantially closed, solves this problem.

3,237,548 Patented Mar. 1, 1966 However, with the advent of airconditioning, need for a type of hood was dictated which could beoperated without drawing large quantities of air from the room in whichit was installed, the ideal hood, of course, being one which couldsupply its own air and would draw no air out of the room in which it wasinstalled. Hoods have been developed which minimize the withdrawal ofroom air and are called air conditioning fumehoods. An example of such ahood is the one shown in United States Letters Patent No. 3,000,292issued September 19, 1961, on application of C. A. Wojan.

In principle, these hoods supply air through an intake duct or port. Theair is then removed through the exhaust port. In such hoods, there is nogrille, and the glass sash may be substantially closed without affectingthe velocity of the exhaust system. Such hoods work well with the sashclosed. However, when the sash is opened, there is sometimes undesirableleakage of noxious fumes from the working chamber into the room,especially from the lower part of the working chamber.

In a hood without a by-pass, the face velocity increases to anundesirable speed as the sash is lowered, especially when the originalface velocity is high. Such high face velocity is undesirable for manyreasons; for example, hot plates are cooled off too rapidly, Bunsenburners are upset, and Bunsen burner flames are put out. In addition,delicate balances within the hood enclosure are disturbed, and delicatesetups are in danger of being upset. This problem was partially solvedin a laboratory fumehood disclosed in United States Letters Patent No.2,819,- 666 issued January 14, 1958, on application of George L. McNeilet al., by providing for the auxiliary air to be supplied from chambershaving a nozzle opening directing the auxiliary air outside of the openface opening of the device when the sash was up, or directly into theworking chamber of the device by means of a by-pass port when the sashwas down. While the construction of McNeil et al. overcomes the problemof face velocity increasing as the sash is closed, the problem stillremained as to how to furnish the auxiliary air in an air conditionedfumehood without permitting it to be blown directly on the operator whostands in front of the face opening, and also to provide it particularlyat the lower part of the face opening where there was greater danger ofnoxious fumes escaping during the operation of the hood.

It is therefore an object of this invention to provide a fumehood havingauxiliary air supply in which the auxiliary air is supplied to thedevice from outside of the top and sides of the circumference orperimeter around the sash opening of the device, without interferingwith the operator of the device, and to provide a fairly evendistribution of auxiliary air from directly outside the sash or faceopening of the device, when the sash is open, to minimize as much aspossible the use of room air through the sash opening, and to prevent asmuch as possible the escape of noxious fumes out of the said sashopening.

It is another object of this invention to provide such an auxiliary airsupply having means to adjust or control the distribution and flow ofthe auxiliary air to conform to the conditions of the size, and aircurrents, of the room or place in which the said hood is installed.

It is another object of this invention to provide a fumehood having anauxiliary air supply in which a portion of the auxiliary air isintroduced into the device at the forward portion of the floor or tablethereof to carry the heavier-than-air gases directly into the exhaustchamber and out of the fumehood.

It is a further object of this invention to provide such a device inwhich the desired face velocity does not increase to an undesirablespeed by providing an air by-pass for the auxiliary air.

Further objects and advantages will appear in the specificationhereinbelow. These objects and advantages are achieved in the forms ofthe invention illustrated in the accompanying drawings in which:

FIG. 1 is a face view of the apparatus with parts cut away to showbaflies and air flow currents with sash up;

FIG. 2 is a view similar to FIG. 1 with sash down to show the reversetrend of air flow;

FIG. 3 is a section along the lines 3-3 in FIG. 1;

FIG. 4 is a section along the lines 44 in FIG. 2;

FIG. 5 is a section along the lines 55 in FIG. 3;

FIG. 6 is a section of the device along the lines 6-6 in FIG. 1, withportions cut away;

FIG. 7 is an elevational detail of an alternate form of grille of a sideconduit;

FIG. 8 is an elevational detail of a further alternate form of grille ofa side conduit; and

FIG. 9 is a detail of a flap of the invention in elevation.

Similar numerals refer to similar parts throughout the several views.

It is an important object in all fumehoods to move a large velocity airthrough the sash opening from the outside away from the operator intothe hood. The rate of the movement of such air through the sash openingmay be termed face velocity. It is very important to have the auxiliaryair come from outside the sash because otherwise if the air comes frominside the sash opening, the most critical portion of the fumehood, thatportion nearest the operator, is not cleared properly. For example, ifit is desired to have a fumehood with a face velocity of 100 feet perminute at the sash opening, if air is supplied from inside the hood, itwill move the high point of the velocity inside the hood, and there willbe a minimum face velocity through the sash opening. By pro viding theauxiliary air at the outside top and sides of the sash opening, it issupplied outside of the plane (sash opening) where the highest velocityis desired, and creates this desired face velocity.

It is to be understood, of course, that the speed of the face velocityis controlled by the combined action of the suction or exhaust blower ofthe hood at the suction end of the hood and the auxiliary air blowerpushing air through the openings outside the sash opening.

The fumehood may be constructed of any material strong enough for thepurpose. It is also desirable for the construction material to befireproof and for the floor or counter of the device to be acidresistant.

A main frame 10 is therefore provided, made of enameled steel coatedwith acid resistant paint. The floor or counter 11 should be of materialsuch as stone, and suffi ciently thick to withstand acids, heat anddamage reactions. The floor 11 may be a separate counter top over whichthe main frame 10 of the hood is placed, or it may be an integral partof the hood construction; or in another form of the device, such as alarger floor model, it could rest directly on the floor of a room ratherthan on a table, in which case the floor of the room could act as thecounter or floor of the device.

The main housing 10 has a rear wall 12, a pair of side walls 14 and 15,a front wall 16 and a top 17. A working chamber 18 is formed between thefloor 11, inner side walls 20 and 22 and an internal baffle 24. Anexhaust chamber 26 is formed between the internal baffle 24, the sidewalls 20 and 22 and the rear wall 12. The working chamber 18 and theexhaust chamber 26 are connected by upper and lower exhaust apertures 28and 30 respectively. The front of working chamber 18 is formed partiallyby the rear wall 32 of an auxiliary air chamber 34 and partially by thesash 36. The auxiliary air cham ber 34 is formed between rear wall 32,side walls 14 and 15 and front wall 16, and communicates with theworking chamber 18 through a by-pass 38. The sash 36 is provided with apane of safety glass or wired glass 40, and is adapted to slide up anddown within sash guides 42 and 44. There is an inner face opening forthe working chamber 18 in the plane substantially corresponding to sashguides 42 and 44. The inner face opening 50 is at the lower part of thedevice, and is beneath and to the rear of front wall 16. The height ofthe sash 36 should be sufficient to cover the inner face opening 50 whenthe sash 36 is completely lowered. The sash 36 may be maintained atvarious positions by balancing means such as a counterweight or sashbalance (not shown) installed in any manner known to the art of hangingwindows. The auxiliary air chamber 34 has a bottom wall 52 having anumber of openings 54 and a flanged back portion 56. The back portion56, together with rear wall 32, with bypass 38 between them, forms acommon dividing structure between the auxiliary air chamber 34 and theworking chamber 18, forming at the same time the rear of the auxiliaryair chamber and the upper portion of the front of the working chamber18. The device has a bottom conduit 58 formed by a floor extension 60, afoil 62 and the lower portion of the side walls 14 and 15. The bottomconduit 58 communicates with the auxiliary air chamber 34 by means ofside conduits 64 and 66.

Side conduit 64 is comprised of side wall 14, internal partition 68, alower leg of front wall 16, and an inner face wall 72. Side conduit 66is comprised of wall 15, internal partition 76, lower leg 78 of wall 16,and inner face wall 80.

An exhaust collar 82 is provided in the top 17. Exhaust collar 82communicates with exhaust chamber 26 and may be attached to any suitabletype of duct or other means which should be connected to an exhaustblower (not shown), or other means of moving the air out of the exhaustchamber 26. I do not show the ducts or the exhaust pumps since these arewellknown to the art, and may be any type suitable for the purpose.

An intake collar 84 is provided above the auxiliary air supply chamber34. A suitable duct (not shown) is attached to intake collar 84 andconnected to an input blower (not shown) to provide an auxiliary airinput for the device. Here again, the ducts and the input blowers neednot be shown since these are well known in the art, and may be of anytype suitable for the purpose.

The side conduits have vanes 86 which are located in openings or grilles88 of the inner face walls 72 and respectively. The vanes 86 may bepivotted on pins 90 in sockets located at reference points 93 to providefor swinging movement of the flaps from an open position as shown in theleft hand portion of FIG. 6 of the drawings to a closed position asshown in the right hand portion of FIG. 6 of the drawings. In thedrawings, a single opening 88 is shown on each side of the side conduitcontaining three vanes 86 in each opening. This is submitted by way ofillustration only as there may be any number of openings containing anysuitable number of vane means.

The grille openings 88 have the vanes 86 to cover or, close selectedportions of the grille openings. These vanes 86 may be individuallyadjusted, or they may be connected together to a single control in anymanner known to the art. The grille openings 88 and vanes 86 may beeither horizontal or verticle, or in any formation suited to theconstruction of the device.

It is preferred to put in verticle vanes 86 hinged by means of the pins90 which may be closed by turning them inwardly toward the sash opening50, since vanes 86 which close by turning inwardly toward inner faceopening 50, would act as deflectors to deflect the supply of auxiliaryair toward the sash opening 50 when they were partially closed.

It may be preferable to leave all of the vanes 86 to be individuallyadjusted since adjustment for each of the vanes 86 depends upon theposition of the device 10 in' a room, the size of the room, the aircurrents in the room, proximity of air conditioning vents, proximity ofhot air blowers, and other factors. Once the device 10 is installed in aroom, and the vanes 86 are set, in accordance with the desires of theengineer or operator adjusting same, they will probably remain set untilthere is a change in one of the factors of the room and the air currentsto require further adjustment.

The grilles or openings 88 at the inner sides of the side conduits 64and 66 may be made in alternate form without vanes 86, or in furtheralternate form, with panels 91 containing perforated steel mesh 92, orpanels 94 containing holes 96, such panels having various proportions ofopen area. In these forms of invention, the openings (mesh 92) or (holes96) in the side openings 88 would be precalculated as to size and numberat the factory since there would be no adjustment means. For example, ifit were desired to have a hood installation where a greater volume ofauxiliary air had to be moved into the bottom conduit 58 through thegrille or aperture 100 at the rear of the bottom conduct 58 across thefloor 11, then the side openings would be relatively few and/ or small.On the other hand, if it were desired to have a greater volume of aircoming through the side conduits 64 and 66 at the sides of the outsideof inner face opening 50, then the side openings would be relativelygreater in number and/or larger. This will be more readily understoodwhen the action of the air currents with the sash up and down areexplained hereinbelow.

The grille or aperture 100 at the rear of bottom conduit 58 does nothave a closure adjustment since it is desirable to have a constant flowof auxiliary air from grille 100 across the bottom of the devices toexhaust aperture 30 to clear off heavier-than-air gases that may fall tothe floor 11 of the device.

A series of baffles 102 have been provided underneath the input cap- 84to deflect the auxiliary air coming into the device, which wouldnormally go straight down and through the openings 54 at the bottom ofauxiliary air chamber 34, to the side conduits 64 and 66. These baflies102' are placed directly in the'way of the stream of auxiliary air (seeFIG. 1 of the drawings'and FIG. 5 of the drawings) and Will'cause someof the air to move to each side of the device and then down through theside conduits 64 and 66 to the bottom conduit 58.

I refer now to FIGS. 1, 3 and 5 of the drawings where the sash 36 is inup position. The pane 40 of the sash 36 covers by-pass opening 38. Theinner face opening 50 is completely open. Let us assume that an inputblower is blowing auxiliary air into input collar 84 of the device, andan exhaust blower is pulling exhaust air from exhaust collar 82 of thedevice. This creates air currents as shown by means of the arrows inFIGS. 1, 3 and 5 of the drawings. Air will come down through collar 84into auxiliary chamber 34. Most of the air will go down through theopenings 54 at the bottom of the auxiliary chamber, and then throughface opening 50 to be exhausted through either the top or bottom exhaustapertures 28 and 30, through exhaust chamber 26 and out of collar 82.Some of the air will be baffied off by baffles 102 into side conduits 64and 66 and come out through side openings 88 as shown by the arrow inthe mentioned figures, and into the face opening 50, thence to workingchamber 18 to be exhausted through exhaust apertures 28 and 30, exhaustchamber 26 and out of collar 82. Some of the air will go completely downinto the bottom conduit 58, through grille 100, across the bottom of thedevice at fioor 11, through exhaust aperture 30 to exhaust chamber 26,and out of the device at exhaust collar 82.

As was stated above, the amount of air which will go through either ofthe mentioned paths may be determined by adjusting the vanes 86 of thedevice. When the flaps are in a more open position, more of the air willgo through the side conduits, and when the flaps are in a more closedposition, more of the air will go through bottom grille 100. It will beappreciated at this point that the inner face opening 50 is at the innerside of an imaginary oblong formed between the plane of the inner faceopening 50 and the plane of an outer face opening 104, and that theentire imaginary oblong including outer face opening 104 and inner faceopening 50 comprises a form of face opening means for the device. Theends of the oblong would be formed by the foil 62 on the bottom, thebottom wall 52 of the auxiliary air chamber 34, and the inner sides 72and 80. Thus, all of the auxiliary air of the device which is suppliedfrom outside of the inner face opening is contained within the imaginaryoblong between planes 104 and 50. The entire inner face opening 50 willhave face velocity currents throughout its entire area from air suppliedfrom within this imaginary oblong inside of the outer face opening 104and directly outside of inner face opening 50. None of this auxiliaryair will be directed toward the operator or person standing in front ofouter face opening 104. At the same time, there will be an internalstream of auxiliary air from grille toward exhaust aperture 30 to coverthe bottom of the device and prevent escape of heavier-than-air gases.The net result is that a face velocity covering the entire inner faceopening may be maintained so that, while the sash is up, there will beno stray currents moving against the desired flow permitting noxiousgases to escape from the hood.

When the sash is down as shown in FIGS. 2 and 4 of the drawings, theauxiliary air will come down through the collar 84 into the auxiliarychamber 34, then through the by-pass opening 38 which is now uncoveredwhen the sash 36 and pane 40 are in down position. The principal airflow will then be through by-pass opening 38 into working chamber 18 andout through exhaust apertures 28 and 30 to exhaust chamber 26 and upthrough exhaust collar 82. There will also be a slight reverse flow atthe bottom openings 54 of auxiliary chamber 34 into the working chamber18 through by-pass 38, and there will be some reverse flow from outsideof the device into the grille openings 88 .and into side conduits 64 and66, most of which will go up into auxiliary chamber 34 and through theby-pass 38 into the working chamber 18, and some of which will gothrough bottom conduit, out of grille 100, across floor 11 to exhaustaperture 30.

When sash 36 is down against the foil 62 closing the inner face opening50, the described reverse flow from outside the device will result bydesign because the exhaust blower is set to pull slightly more cubicfeet per minute of air than the .auxiliary blower is set to push intothe device. This differential causes the reverse flow as shown anddescribed when the sash 36 is down. This reverse flow is desirable toprevent escape of noxious fumes from the device when the sash is downand is adjusted to remove the least amount of room air necessary forthis purpose.

The space between double walls 14 and 20 and double walls 15 and 22 maybe utilized for auxiliary equipment such as electric wiring or otherapparatus. It is not functional insofar as the device as shown anddescribed is concerned.

The fumehood described herein has the advantage of using a minimum ofroom air, it does not blow air on the operator outside of the device,and effectively prevents the escape of noxious fumes when the sash isup.

While I have described my device in its preferred forms, there are otherforms which it may take without departing from the spirit and scope ofthe invention, and I therefore desire to be protected for all formscoming within the scope of the claims hereinbelow. For example, thebottom wall 52 of the auxiliary air chamber 34 may be horizontal asshown or be inclined at an angle in either direction to furnishadditional grille. area through the openings 54 should this be desired.

Wherefore I claim:

1. A fumehood having a main housing comprising a working chamber definedby at least one wall including face opening 'means at the front thereof;an auxiliary chamber located in front of said working chamber and abovesaid face opening means having a rear portion common with the upper partof the front of said working chamber having at least one interchamberopening between the said working chamber and the said auxiliary chamberabove the said face opening means; closure means comprising slideablepanel means being at least as large in area as said face opening meansand adapted to be moved on guide means in the main housing to selectedpositions relative to said face opening means and said interchamberopening, so that when said closure means is moved from said face openingmeans to said interchamber opening, said face opening means will beprogressively uncovered and said interchamber opening will beprogressively covered; said working chamber having exhaust meansincluding at least one exhaust aperture for exhausting gases, and saidauxiliary chamber having input blower means to provide auxiliary air tothe auxiliary chamber; said auxiliary chamber having a bottom Wallportion comprising at least one opening below said interchamber openingoutside of and above the said face opening means, and said workingchamber having transverse aperture means at a front wall portion thereofbeneath said face opening means in a position facing toward the rear ofsaid working chamber and relatively near the lowest portion of the wallof said working chamber, said transverse aperture means being connectedthrough conduit means to said input blower means of said auxiliarychamber.

2. The fumehood as described in claim 1, in which the exhaust means forthe said working chamber comprises at least one exhaust aperture meanspositioned at the lower rear of the working chamber and at least oneexhaust aperture means positioned at an upper portion of the workingchamber, said exhaust aperture means being connected to exhaust blowermeans through conduit means.

3. A fumehood having a main housing comprising a working chamber definedby at least one wall including face opening means at the front thereof,an auxiliary air chamber comprising front, rear and bottom wall portionsand positioned at the upper part of the front of the working chamberhaving a pair of conduits depending therefrom positioned at the sides ofthe front of the main housing, said conduits having inwardly disposedside wall portions substantially as wide as the bottom wall portion ofthe said auxiliary chamber, and being joined at the bottoms of the faceopening means by a bottom conduit; interchamber opening means comprisingat least one opening between the rear of said auxiliary air chamber andthe said working chamber, said face opening means having a top portiondefined by the bottom wall portion of the said auxiliary chamber, thesides of said face opening means being defined by the inwardly facingside wall portions of the said conduits and the bottom of said faceopening means defined by the top of said bottom conduit thereby formingface opening means having an outer face opening and an inner faceopening, closure means for the said face opening means comprisingslideable panel means being at least as large in area as said inner faceopening and adapted to be moved on guide means in the main housingbehind the said inner face opening to selected positions relative tosaid inner face opening and said interchamber opening means so that whensaid closure means is moved from said inner face opening to saidinterchamber opening, said inner face opening will be progressivelyuncovered and said interchamber opening will be progressively covered,said bottom wall portion of the said auxiliary chamber as well as saidinwardly facing side wall portions of said conduits having aperturemeans spaced between said outer face opening and said inner faceopening, with said bottom conduit having aperture means communicatingwith the inside of said working chamber at a position substantially nearthe lowest portion of the wall of the said working chamber, and exhaustmeans comprising at least one exhaust aperture in the working chamber.

4. The fumehood as described in claim 3, in which. the exhaust means forthe said working chamber comprises at least one exhaust aperturepositioned at the lower rear of the working chamber and at least oneexhaust aperture positioned at an upper portion of the Working chamber,said exhaust apertures being connected to exhaust blower means throughconduit means.

5. The fumehood as described in claim 3, in which the aperture means, ofthe said side conduits spaced between the said outer and inner faceopenings of the said face opening means, are provided with vane means,

6. The fumehood as described in claim 3, in which the aperture means, ofthe said side conduits spaced between the said outer and inner faceopenings of the said face opening means, are provided with panel meanshaving a plurality of openings therein.

7. The fumehood as described in claim 3, in which the aperture means, ofthe said side conduits spaced between the said outer and inner faceopenings of the said face opening means, are provided with panel meanscomprising a mesh material having openings therein.

References Cited by the Examiner UNITED STATES PATENTS 2,549,042 4/ 1951Augermueller 981l5 3,021,776 2/1962 Kennedy 98-115 3,111,077 11/1963Cortright 98-115 WILLIAM F. ODEA, Primary Examiner.

JOHN F. OCONNOR, Examiner.

1. A FUMEHOOD HAVING A MAIN HOUSING COMPRISING A WORKING CHAMBER DEFINEDBY AT LEAST ONE WALL INCLUDING FACE OPENING MEANS AT THE FRONT THEREOF;AN AUXILIARY CHAMBER LOCATED IN FRONT OF SAID WORKING CHAMBER AND ABOVESAID FACE OPENING MEANS HAVING A REAR PORTION COMMON WITH THE UPPER PARTOF THE FRONT OF SAID WORKING CHAMBER HAVING AT LEAST ONE INTERCHAMBEROPENING BETWEENT THE SAID WORKING CHAMBER AND THE SAID AUXILIARY CHAMBERABOVE THE SAID FACE OPENING MEANS; CLOSURE MEANS COMPRISING SLIDEABLEPANEL MEANS BEING AT LEAST AS LARGE IN AREA AS SAID FACE OPENING MEANSAND ADAPTED TO BE MOVED ON GUIDE MEANS IN THE MAIN HOUSING TO SELECTEDPOSITIONS RELATIVE TO SAID FACE OPENING MEANS AND SAID INTERCHAMBEROPENING, SO THAT WHEN SAID CLOSURE MEANS IS MOVED FROM SAID FACE OPENINGMEANS TO SAID INTERCHAMBER OPENING, SAID FACE OPENING MEANS WILL BEPROGRESSIVELY UNCOVERED AND SAID INTERCHAMBER OPENING WILL BEPROGRESSIVELY COVERED: SAID WORKING CHAMBER HAVING